An organic light emitting diode (OLED) is an organic thin film electroluminescent device. It has advantages of having a simple fabricating process, a low cost, high luminous efficiency, easily forms a flexible structure, and has a wide viewing angle. Thus, the display technology in which the organic light emitting diode is applied has become an important display technology.
Currently, an OLED display device can be divided into a top-emitting type, a bottom-emitting type, and a double-side-emitting type, based on the light emitting direction. For all types of OLED display devices, it is generally required that one of the cathode and anode be made from a transparent material, so that light can be emitted through the electrode made from the transparent material.
For example, in an array substrate for a top-emitting OLED, the cathode is made from indium tin oxide (ITO) of high resistivity, an anode made of a metallic material, and a functional layer of an organic material therebetween. The functional layer emits light which is emitted outside through the transparent cathode.
Since the transparent ITO has a relatively high resistivity, the cathode suffers from a drop in voltage, which adversely affects the performance of the OLED display device.
In the prior art, a patterned metal layer is formed on a package substrate of the OLED display device, and an ITO layer is formed to contact the metal layer and further contact the ITO cathode of the OLED array substrate to improve resistivity of the cathode. However, this method is complicated to fabricate, which leads to an increase in cost and a decrease in productivity.